def countdown(i):
    print(i)
    if i <= 0:  # 基线条件
        return
    else:  # 递归条件
        countdown(i - 1)


# 3.3.1
def greet(name):
    print('hello,' + name + "!")
    greet2(name)
    print("getting ready to say bye...")
    bye()


def greet2(name):
    print("how are you, " + name + "?")


def bye():
    print("ok bye!")
